1. Field of the Invention
The present general inventive concept relates to an image pickup apparatus. More particularly, the present general inventive concept relates to a zoom lens optical system usable in an image pickup apparatus.
2. Description of the Related Art
A zoom lens optical system is an optical system that can change a focal length to enlarge or reduce an image corresponding to an object. In order to achieve high zoom magnification and to reduce aberration that is generated in the zoom lens optical system, a plurality of lenses are combined and used in the zoom lens optical system. Accordingly, the zoom lens optical system is larger and heavier than a single focus optical system.
Recently image pickup apparatuses which use a zoom lens optical system, such as digital still cameras, video cameras, and the like, have been widely distributed and used. Therefore, for users' convenience, many efforts to develop more compact and more lightweight image pickup apparatuses have been made. Depending on to the trend, the zoom lens optical systems are required to be miniaturized and lightweight.
Also, for photographing under low illumination, it is preferable to provide a brighter optical system, that is, an optical system having a small F number. Therefore, it is a trend that the optical system of the image pickup apparatus has a large diameter. However, in this case since the size of an aperture thereof also becomes bigger, a shutter speed thereof becomes slower. Accordingly, technology is required to improve the shutter speed in the optical system of the image pickup apparatus which may have a large diameter.